InAs-based quantum dots(QDs)are promising heavy-metal-free semiconductors for infrared emission technologies,offering tunable bandgaps via quantum confinement and excellent charge-carrier transport properties.Building...InAs-based quantum dots(QDs)are promising heavy-metal-free semiconductors for infrared emission technologies,offering tunable bandgaps via quantum confinement and excellent charge-carrier transport properties.Building on these advantages,we report the synthesis of QDs tailored for emission in the near-infrared(NIR)and short-wave infrared(SWIR)regions,emphasizing the critical role of capping ligands in controlling surface facet populations and nanocrystal morphology.Specifically,we demonstrate that the choice of ligand plays a critical role in determining the morphology and surface characteristics of InAs QDs.Using dioctylamine as a ligand results in InAs QDs with a spherical or tetrapod morphology,where nonpolar(110)facets are predominantly exposed on the surface.In contrast,oleic acid as a ligand promotes the formation of tetrahedralshaped QDs with polar(111)crystalline planes being more prominently exposed.Using a one-pot synthesis approach,we successfully synthesized InAs/InZnP/ZnSe/ZnS core-multi-shell structures that effectively minimize interfacial defects.QDs with dioctylamine-capped core exhibit significantly higher photoluminescence quantum yield(PLQY)compared to those with oleic acid-capped cores.We achieved a PLQY of 39%at 1260 nm and 7.3%at 1420 nm with QDs using dioctylamine,representing efficiency values among the best reported in both the NIR and SWIR regions.Transient absorption(TA)spectroscopy reveals that dioctylaminecapped QDs exhibit reduced ground-state bleaching differences across excitation wavelengths compared to oleic acid-capped QDs,indicating significantly reduced interfacial trap states.These findings highlight the importance of ligand-driven facet control in the context of minimizing interfacial defect formation.展开更多
Metal halides show great promise as a new generation of near-infrared(NIR)light-emitting materials.Compared with other light-emitting materials,double perovskites possess structures with different dimensionalities,whi...Metal halides show great promise as a new generation of near-infrared(NIR)light-emitting materials.Compared with other light-emitting materials,double perovskites possess structures with different dimensionalities,which can support multiple emission centers,leading to varied photoluminescence.Among various doping centers,ytterbium(Ⅲ)(Yb^(3+))has attracted attention because of its unique twoenergy-level structure(^(2)F_(5/2) and ^(2)F_(7/2)).However,the NIR emission of Yb^(3+)remains unsatisfactory because of poor resonance energy transfer between Yb^(3+)and sensitizers.Here,effective NIR-emitting lead-free perovskites are developed by co-doping antimony(Ⅲ)(Sb^(3+))and lanthanide(Ⅲ)ions into Cs2NaInCl6.Under excitation at 318 nm,Cs_(2)NaInCl_(6):Sb^(3+)/Yb^(3+)showed a broadband NIR emission peak at 1001 nm,whereas Cs_(2)NaInCl_(6):Sb^(3+)/Nd^(3+)exhibited three NIR emission peaks at 896,1077,and 1358 nm.The exciton dynamics of the materials were investigated.Experiments and density functional theory calculations revealed that the NIR emission of Yb^(3+)originated from a charge-transfer state(CTS)and energy transfer,whereas that of Nd^(3+)arose from resonance energy transfer.Profiting from the high-energy selftrapped exciton(STE)emission and CTS with Yb^(3+),a high photoluminescence quantum yield of 48.95%was realized.The excellent NIR luminescence performance combined with high environmental stability demonstrates the potential of these metal halides for use in night-vision technologies.展开更多
The exploration of high-performance near-infrared phosphors has attracted widespread attention.In this work,a brand new Rb2LiAlF6:Cr^(3+)(denoted as RLAF:Cr)phosphor has been constructed by the substitution of Al^(3+)...The exploration of high-performance near-infrared phosphors has attracted widespread attention.In this work,a brand new Rb2LiAlF6:Cr^(3+)(denoted as RLAF:Cr)phosphor has been constructed by the substitution of Al^(3+)ions with Cr^(3+)ions.Evidence shows that two sets of near-infrared emission bands,which originated from two types of Cr^(3+)sites,were observed upon blue light excitation.These emission bands merged into a wide emission band locating in the region of 650 nm-1050 nm,with a full width at half maximum(FWHM)of 125 nm.In addition,a high quantum efficiency of 77.7%and an excellent thermal stability at 417 K,with a retention rate of 90.5% of that at room temperature(RT),were witnessed.Profiting from the luminescence properties of the NIR phosphor,clear images of biological tissues and human palm veins were obtained using a light-emitting diode(LED)as a lighting source,which was constructed using an RLAF:Cr phosphor and a blue InGaN chip.These images showed the large potential of the RLAF:Cr phosphor for night vision and bioimaging in LED devices.展开更多
A breakthrough in the luminescence performance of broadband near-infrared (NIR) emitting phosphors is central to their successful application in next-generation smart NIR light sources. Currently,due to the deficiency...A breakthrough in the luminescence performance of broadband near-infrared (NIR) emitting phosphors is central to their successful application in next-generation smart NIR light sources. Currently,due to the deficiency of phosphors that have both high blue light absorption efficiency (AE) and high NIR internal quantum efficiency (IQE),NIR phosphor-converted LEDs (pc-LEDs) still bear low external quantum efficiencies (EQE) (<40%). In this work,an effective ion substitution strategy,that is Nb^(5+) substitution for Ta^(5+),was used to improve the luminescence of GaTaO_(4) (GTO):0.02Cr^(3+) phosphor. Consequently,a series of GaTa_(1-y)Nb_(y)O_(4) (GTNO):0.02Cr^(3+) (y=0–1.0) solid solution phosphors achieved breakthroughs in the AE,IQE and EQE. Under 474 nm excitation,the AE,IQE and EQE of the GTNO:0.02Cr^(3+) (y=0) phosphor were 39.9%,75.4% and 30.1%,respectively. After the proper substitution of Nb^(5+),corresponding to GTNO:0.02Cr^(3+) (y=0.5),the three values were accordingly enhanced to 52.5%,94.0% and 49.4%,under 476 nm excitation. The ion substitution strategy gave significant breakthroughs in the luminescence efficiency of the NIR phosphors,which is an important guideline for the development of more efficient broadband NIR phosphors in the future.展开更多
Near-infrared(NIR)luminescence materials are ideal candidates for applications in three-dimensional biomedical imaging and night vision.Here,we constructed an ultra-broadband NIR material based on LiBaF3:Ni^(2+)single...Near-infrared(NIR)luminescence materials are ideal candidates for applications in three-dimensional biomedical imaging and night vision.Here,we constructed an ultra-broadband NIR material based on LiBaF3:Ni^(2+)single crystals with NIR emission at 1400 nm and a full width at half maximum(FWHM)of 254 nm from 1100 to 1700 nm wavelengths,covering the NIR-II and NIR-Ⅲ regions.Through the activation of inactive Mg^(2+),the NIR emission could be improved by a factor of two,and the FWHM enhanced to 273 nm.This is ascribed to the lattice distortion by the addition of Mg^(2+)as well as the charge asymmetry between the Mg^(2+)and Li+ions.The prepared Ni^(2+)/Mg^(2+)-doped NIR perovskite single crystals were packaged with a commercial high-efficiency near-ultraviolet LED chip(@395 nm)to construct NIR single-crystal LEDs,and their promising applications with high efficiency were demonstrated in NIR night-vision monitoring and vein non-destructive imaging.展开更多
Short-wave infrared(SWIR)phosphor-converted light-emitting diodes(pc-LEDs)are promising for biomedical and nondestructive applications.Still,their progress is constrained by the lack of efficient,ultra-broadband phosp...Short-wave infrared(SWIR)phosphor-converted light-emitting diodes(pc-LEDs)are promising for biomedical and nondestructive applications.Still,their progress is constrained by the lack of efficient,ultra-broadband phosphors excitable by low-cost blue LEDs.Cr^(3+)-activated materials exhibit strong blue light excitation,but their emission is primarily confined to the NIR-I region.In contrast,Ni^(2+)has the potential to achieve SWIR emission,yet suffers from weak absorption in the blue-light region.In this study,Y_(3)Al_(3)MgSiO_(12):Ni^(2+)and Y_(3)Al_(3)MgSiO_(12):Cr^(3+)–Ni^(2+)phosphors were synthesized.Compared to previous reports,the Y_(3)Al_(3)MgSiO_(12):Cr^(3+)–Ni^(2+)phosphor in this study achieved three significant advancements:(1)efficient energy transfer from Cr^(3+)to Ni^(2+)was achieved(η=91.6%),resulting in a 10.45-fold enhancement of SWIR emission intensity upon 438 nm blue-light excitation,and the optimal excitation wavelength was shifted to the blue-light region.(2)Ultra-broadband continuous emission spanning the NIR-I to NIR-III regions,with an exceptionally wide FWHM(185+311 nm),was achieved in this phosphor.(3)Remarkably high thermal stability was achieved for the NIR-II–III emission in a region where strong electron–phonon coupling and poor thermal stability are typically observed.The underlying mechanism was elucidated through analysis of the crystal structure rigidity and the Huang–Rhys factor(S).A SWIR pc-LED device was further fabricated by integrating the phosphor with a 450 nm blue LED chip,confirming its application potential in covert information recognition and nondestructive detection scenarios.This study not only introduces a broadband SWIR-emitting material system excitable by blue light but also provides a novel strategy for developing efficient and thermally stable SWIR phosphors.展开更多
In recent years,near-infrared phosphor-converted light emitting diodes(NIR pc-LEDs)have been emerging as a promising compact and efficient NIR light source for a variety of applications such as sensing,bioimaging and ...In recent years,near-infrared phosphor-converted light emitting diodes(NIR pc-LEDs)have been emerging as a promising compact and efficient NIR light source for a variety of applications such as sensing,bioimaging and food analysis.However,the development of broadband NIR phosphors with both high emission efficiency and excellent photoluminescence(PL)thermal stability is still facing a great challenge.展开更多
Realizing Sb^(3+)-activated efficient broadband near-infrared(NIR)emission under blue light excitation remains a significant challenge in lead-free metal halides.To overcome the above difficulties,a coordination struc...Realizing Sb^(3+)-activated efficient broadband near-infrared(NIR)emission under blue light excitation remains a significant challenge in lead-free metal halides.To overcome the above difficulties,a coordination structure modulation strategy was adopted,and the broadband NIR emission under blue light excitation was achieved in Sb^(3+)-doped zero-dimensional(0D)organic tin(Ⅳ)bromide.展开更多
High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared...High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared source structure based on an electron-phonon coupling and emitting mechanism.A series of electrical characterizations including carrier mobility[11,361.55 cm^(2)/(V.s)],pulse current(30 ms response time),and cycling stability(2000 cycles)modulated by polarized film was provided.展开更多
The enduring enigma surrounding the near-infrared(NIR)emission of Mn^(2+)continues to ignite intense academic discussions.Numerous hypotheses have emerged from extensive research endeavors to explain this phenomenon,s...The enduring enigma surrounding the near-infrared(NIR)emission of Mn^(2+)continues to ignite intense academic discussions.Numerous hypotheses have emerged from extensive research endeavors to explain this phenomenon,such as the formation of Mn^(2+)-Mn^(2+)ion pairs,Mn^(2+)occupying cubically coordinated sites,as well as conjectures positing the involvement of Mn3+oxidized from Mn^(2+)or defects.Despite these diverse and valuable insights,none of the hypotheses have yet achieved broad consensus.In this study,we have observed prolonged fluorescence lifetimes(~10ms)for the NIR emissions of Mn^(2+)ions,hinting at these ions occupying the high-symmetry octahedral sites inherent to the garnet lattice.This inference is supported by the corroborating results from X-ray absorption fine structure analysis and first-principles calculations.The intense crystal field of octahedral sites,similar to that of AlO6,facilitates the splitting of d-d energy levels,thereby inducing a red-shift in the emission spectrum to the NIR region due to the transition ^(4)T_(1)(4G)→ ^(6)A_(n)(6S)of isolated Mn^(2+).Our findings not only offer a plausible rationale for the NIR emission exhibited by other Mn^(2+)-activated garnet phosphors but also pave a definitive route towards understanding the fundamental mechanisms responsible for the NIR emission of Mn^(2+)ions.展开更多
Unidentified Infrared emission bands (UIBs) are infrared discrete emissions from circumstellar regions, interstellar media (ISM), star-forming regions, and extragalactic objects for which the identity of the emitting ...Unidentified Infrared emission bands (UIBs) are infrared discrete emissions from circumstellar regions, interstellar media (ISM), star-forming regions, and extragalactic objects for which the identity of the emitting materials is unknown. The main infrared features occur around peaks at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with the photon’s rest energy at the peaks 0.376, 0.200, 0.161, 0.144, 0.111, and 0.098 eV, respectively. The UIB emission phenomenon has been studied for about forty five years. The prevailing hypothesis is that the materials responsible for UIB are polycyclic aromatic hydrocarbon (PAH) molecules. PAHs are thought to be one of the main forms in which carbon exists in space. And yet, not a single member of this group of compounds had been identified in space definitively until now [1]. In frames of Hypersphere World-Universe Model (WUM), we introduced Dark Matter (DM) particles, named DIONs, with the rest energy 0.199 eV and an energy density of 68.8% of the total energy density of the World. DIONs compose Outer shells of DM Supercluster’s Cores—the main objects of the World [2]. In this paper, we give an explanation of UIB emission based on the self-annihilation of DM particles DIONs and biDIONs (DIONs pairs) with a rest energy about 0.38 eV that depends on the binding energy. To the best of our knowledge, WUM is the only cosmological model in existence that is consistent with UIB emission phenomenon.展开更多
A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed st...A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.展开更多
A kind of far infrared radiation ceramics was prepared by using silicate minerals, calcium carbonate and silicon dioxide as main raw materials, and cerium nitrate as additive. The structure of the ceramics and far inf...A kind of far infrared radiation ceramics was prepared by using silicate minerals, calcium carbonate and silicon dioxide as main raw materials, and cerium nitrate as additive. The structure of the ceramics and far infrared radiation properties on the surface tension of water were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and a tensiometer, respectively. It was showed that, after being sintered at 1160 ℃, the solid solution was formed by CeO2 and Fe2O3, thus the crystal parameters （c/a axis ratio） and interplanar spacing of Fe2O3 increased. The addition of cerium was regarded to improve the far infrared radiation of ceramics, and the maximum emissivity value in the range of 5-20 μm was 0.94. The surface tension of water gradually decreased with increasing radiation time.展开更多
LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicle...LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicles.Nevertheless,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one step.XRD analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,respectively.Heat treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two samples.The stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute elements.Intriguingly,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA samples.The emissivity of all samples remains above 0.95 from 6 to 10μm.In the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds 0.85.The UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μm.In a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),is a promising candidate in thermal protection coatings of hypersonic vehicles.展开更多
NiCr2O4（NCO）spinel composites with different Mn/Ni atomic ratios（Mn/Ni=0.05,0.10,0.15,and 0.20）were synthesized via solid state reaction method.Phase compositions and microstructure of samples were characterized b...NiCr2O4（NCO）spinel composites with different Mn/Ni atomic ratios（Mn/Ni=0.05,0.10,0.15,and 0.20）were synthesized via solid state reaction method.Phase compositions and microstructure of samples were characterized by X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The TG-DSC curves showed that the appropriate baking temperature for Mn-doped NCO spinel preparation was approximately 1 320℃.X-ray diffraction patterns exhibited the formation of NCO spinel with Fd-3m space group.Valence state of the Mn ions was determined from 2p and 3s X-ray photoelectron spectra.Manganese ions were mostly in divalent and trivalent states,and the ratio of Mn^2＋/Mn^3＋was 0.78-0.98.Fourier transform infrared spectroscopy（FTIR）was used to analyze the spectral emissivity of Mn doped NCO spinel.It was revealed that the infrared emissivity of Mn-doped NCO spinel in 1.8-5μm could be significantly enhanced with increasing content of Mn^2＋,reaching as high as 0.9398.Mn-doped NCO spinel showed excellent radiation performance and good prospect in high emissivity applications in the temperature range of 800-1 200℃.展开更多
Transition metal disilicides are widely used as heating elements and infrared emission coatings.However,the limited intrinsic infrared emissivity and high thermal conductivity are the main limitations to their applica...Transition metal disilicides are widely used as heating elements and infrared emission coatings.However,the limited intrinsic infrared emissivity and high thermal conductivity are the main limitations to their applications as infrared emission coatings in the thermal protection system.To cope with these prob-lems,four medium and high-entropy transition metal disilicides,i.e.,(V_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-1),(Nb_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-2),(V_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-1),and(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2),were designed and synthesized by spark plasma sintering method using transition metal binary disilicides as precursors.The introduction of multi-elements into transition metal disilicides not only im-proved the infrared emissivity but also reduced the electrical and thermal conductivity.Among them,(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2)had the lowest electrical conductivity of 3789 S cm-1,which is over one order of magnitude lower than that of MoSi_(2)(50000 S cm^(-1)),and total infrared emissivity of 0.42 at room temperature,which is nearly double of that of TaSi_(2).Benefiting from low electrical conductivity and phonon scattering due to lattice distortion,the medium and high-entropy transition metal disilicides also demonstrated a significant decline in thermal conductivity compared to their binary counterparts.Of all samples,HE-2 exhibited the lowest thermal conductivity of 6.4 W m^(−1)K^(−1).The high-entropy tran-sition metal disilicides also present excellent oxidation resistance at high temperatures.The improved infrared emissivity,reduced thermal conductivity,excellent oxidation resistance,and lower densities of these medium and high-entropy transition metal disilicides portend that they are promising as infrared emission coating materials for applications in thermal protection systems.展开更多
Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and hig...Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding strategy.The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures.Particularly,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved EM wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.Moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles.The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace,weapons,military and wearable electronics.展开更多
Alkali metal(Li, Na, K) doped ZnO powders were synthesized by solid-state reaction at different calcination temperatures and holding time. Effects of holding time and K sources on the infrared emissivity of ZnO were i...Alkali metal(Li, Na, K) doped ZnO powders were synthesized by solid-state reaction at different calcination temperatures and holding time. Effects of holding time and K sources on the infrared emissivity of ZnO were investigated. The structure and surface morphologies of samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The UV-Vis absorption and infrared emissivities were investigated by a UV-Vis spectrophotometer and an infrared emissometer, respectively. XRD patterns confirm the wurtzite structure of the as prepared samples with single phase. Smooth grain surfaces are detected in all doped ZnO samples, while ZnO:Li and ZnO:Na present the aggregation of grains. The redshifts in the optical band-gap are observed in K-, Na-, and Li-doped ZnO with the values 3.150, 3.144, and 3.142 eV. Due to better crystalline quality, ZnO:K shows a lower emissivity than others. The emissivity of K-doped ZnO decreases to the minimum value(0.804), at 1200 °C and holding 2 h. Compared with KNO3 as K source, K2CO3 doped ZnO has lower emissivities.展开更多
Infrared emissivities of Zn0.99-xMn0.01CoxO （x = 0.00, 0.01, 0.03, 0.05） powders synthesized at different calcination temperatures by solid-state reaction are investigated. Their phases, morphologies, UV absorption ...Infrared emissivities of Zn0.99-xMn0.01CoxO （x = 0.00, 0.01, 0.03, 0.05） powders synthesized at different calcination temperatures by solid-state reaction are investigated. Their phases, morphologies, UV absorption spectra, and infrared emissivities are studied by XRD, SEM, UV spectrophotometer, and an IR-2 dual-band infrared emissometer in a range of 8 μm-14 μm. Doped ZnO still has a wurtzite structure, and no peaks of other phases originating from impurities are detected. The optical band-gap decreases as the Co content and calcination temperature ascend, and of which the smallest optical band gap is 2.19 eV. The lowest infrared emissivity, 0.754, is observed in Zn0.98Mn0.01Co0.01O with the increase in Co concentration. The infrared emissivity experiences fluctuations as the calcination temperature increases, and its minimum value is 0.762 at 1100 ℃.展开更多
The stoichiometric vanadium（IV） oxide thin films were obtained by controlling the temperature, time and pressure of annealing. The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 n...The stoichiometric vanadium（IV） oxide thin films were obtained by controlling the temperature, time and pressure of annealing. The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 nm VO2 thin films in the 7.5 μm-14 μm region were discussed. The derived VO2 thin film samples were characterized by Raman, XRD, XPS, AFM, SEM, and DSC. The resistance and infrared emissivity of VO2 thin films under different temperature were measured, and the thermal images of films were obtained using infrared imager. The results show that the VO2 thin film annealed at 550 ℃ for 10 hours through aqueous sol-gel process is pure and uniform. The 900 nm VO2 thin film exhibits better IR thermochromic property than the 400 nm VO2 thin film. The resistance of 900 nm VO2 film can change by 4 orders of magnitude and the emissivity can change by 0.6 during the phase transition, suggesting the outstanding IR thermochromic property. The derived VO2 thin film can control its infrared radiation intensity and lower its apparent temperature actively when the real temperature increases, which may be applied in the field of energy saving, thermal control and camouflage.展开更多
基金supported by the National Research Foundation of Korea(NRF)under Project Numbers RS-2024-00350615,NRF-2021M3H4A3A01062960,and 2022R1A5A1033719the Korea Planning&Evaluation Institute of Industrial Technology(KEIT)under Project Number 20019417,and RS-2024-00440884.
文摘InAs-based quantum dots(QDs)are promising heavy-metal-free semiconductors for infrared emission technologies,offering tunable bandgaps via quantum confinement and excellent charge-carrier transport properties.Building on these advantages,we report the synthesis of QDs tailored for emission in the near-infrared(NIR)and short-wave infrared(SWIR)regions,emphasizing the critical role of capping ligands in controlling surface facet populations and nanocrystal morphology.Specifically,we demonstrate that the choice of ligand plays a critical role in determining the morphology and surface characteristics of InAs QDs.Using dioctylamine as a ligand results in InAs QDs with a spherical or tetrapod morphology,where nonpolar(110)facets are predominantly exposed on the surface.In contrast,oleic acid as a ligand promotes the formation of tetrahedralshaped QDs with polar(111)crystalline planes being more prominently exposed.Using a one-pot synthesis approach,we successfully synthesized InAs/InZnP/ZnSe/ZnS core-multi-shell structures that effectively minimize interfacial defects.QDs with dioctylamine-capped core exhibit significantly higher photoluminescence quantum yield(PLQY)compared to those with oleic acid-capped cores.We achieved a PLQY of 39%at 1260 nm and 7.3%at 1420 nm with QDs using dioctylamine,representing efficiency values among the best reported in both the NIR and SWIR regions.Transient absorption(TA)spectroscopy reveals that dioctylaminecapped QDs exhibit reduced ground-state bleaching differences across excitation wavelengths compared to oleic acid-capped QDs,indicating significantly reduced interfacial trap states.These findings highlight the importance of ligand-driven facet control in the context of minimizing interfacial defect formation.
基金funded by the National Natural Science Foundation of China(Grant No.61874074)Science and Technology Project of Shenzhen(Grant No.JCYJ20220531100815034)Guangdong Basic and Applied Basic Research Foundation(General Program,Grant No.2022A1515012055).
文摘Metal halides show great promise as a new generation of near-infrared(NIR)light-emitting materials.Compared with other light-emitting materials,double perovskites possess structures with different dimensionalities,which can support multiple emission centers,leading to varied photoluminescence.Among various doping centers,ytterbium(Ⅲ)(Yb^(3+))has attracted attention because of its unique twoenergy-level structure(^(2)F_(5/2) and ^(2)F_(7/2)).However,the NIR emission of Yb^(3+)remains unsatisfactory because of poor resonance energy transfer between Yb^(3+)and sensitizers.Here,effective NIR-emitting lead-free perovskites are developed by co-doping antimony(Ⅲ)(Sb^(3+))and lanthanide(Ⅲ)ions into Cs2NaInCl6.Under excitation at 318 nm,Cs_(2)NaInCl_(6):Sb^(3+)/Yb^(3+)showed a broadband NIR emission peak at 1001 nm,whereas Cs_(2)NaInCl_(6):Sb^(3+)/Nd^(3+)exhibited three NIR emission peaks at 896,1077,and 1358 nm.The exciton dynamics of the materials were investigated.Experiments and density functional theory calculations revealed that the NIR emission of Yb^(3+)originated from a charge-transfer state(CTS)and energy transfer,whereas that of Nd^(3+)arose from resonance energy transfer.Profiting from the high-energy selftrapped exciton(STE)emission and CTS with Yb^(3+),a high photoluminescence quantum yield of 48.95%was realized.The excellent NIR luminescence performance combined with high environmental stability demonstrates the potential of these metal halides for use in night-vision technologies.
基金supported by the National Natural Science Foundation of China(grant nos.22365034,22065039,52272174 and U22A20135)the Yunnan Fundamental Research Projects(202101AT070072).
文摘The exploration of high-performance near-infrared phosphors has attracted widespread attention.In this work,a brand new Rb2LiAlF6:Cr^(3+)(denoted as RLAF:Cr)phosphor has been constructed by the substitution of Al^(3+)ions with Cr^(3+)ions.Evidence shows that two sets of near-infrared emission bands,which originated from two types of Cr^(3+)sites,were observed upon blue light excitation.These emission bands merged into a wide emission band locating in the region of 650 nm-1050 nm,with a full width at half maximum(FWHM)of 125 nm.In addition,a high quantum efficiency of 77.7%and an excellent thermal stability at 417 K,with a retention rate of 90.5% of that at room temperature(RT),were witnessed.Profiting from the luminescence properties of the NIR phosphor,clear images of biological tissues and human palm veins were obtained using a light-emitting diode(LED)as a lighting source,which was constructed using an RLAF:Cr phosphor and a blue InGaN chip.These images showed the large potential of the RLAF:Cr phosphor for night vision and bioimaging in LED devices.
基金supported in part by the National Natural Science Foundation of China(grant no.62127816)in part by the National Key R&D Program of China(grant No.2018YFB1801001)+3 种基金in part by the Guangdong Introducing Innovative and Enterpreneurial Teams of“The Pearl River Talent Recruitment Program”(grant no.2019ZT08X340)in part by the Research and Development Plan in Key Areas of Guangdong Province(grant no.2018B010114002)in part by the Science and Technology Program of Guangzhou,China(grant no.202002030091,202102080261)in part by the Guangzhou Key Laboratory of Low Dimensional Materials and Energy Storage Devices(grant no.201905010002).
文摘A breakthrough in the luminescence performance of broadband near-infrared (NIR) emitting phosphors is central to their successful application in next-generation smart NIR light sources. Currently,due to the deficiency of phosphors that have both high blue light absorption efficiency (AE) and high NIR internal quantum efficiency (IQE),NIR phosphor-converted LEDs (pc-LEDs) still bear low external quantum efficiencies (EQE) (<40%). In this work,an effective ion substitution strategy,that is Nb^(5+) substitution for Ta^(5+),was used to improve the luminescence of GaTaO_(4) (GTO):0.02Cr^(3+) phosphor. Consequently,a series of GaTa_(1-y)Nb_(y)O_(4) (GTNO):0.02Cr^(3+) (y=0–1.0) solid solution phosphors achieved breakthroughs in the AE,IQE and EQE. Under 474 nm excitation,the AE,IQE and EQE of the GTNO:0.02Cr^(3+) (y=0) phosphor were 39.9%,75.4% and 30.1%,respectively. After the proper substitution of Nb^(5+),corresponding to GTNO:0.02Cr^(3+) (y=0.5),the three values were accordingly enhanced to 52.5%,94.0% and 49.4%,under 476 nm excitation. The ion substitution strategy gave significant breakthroughs in the luminescence efficiency of the NIR phosphors,which is an important guideline for the development of more efficient broadband NIR phosphors in the future.
基金supported by the National Natural Science Foundation of China(No.62275133)the Natural Science Foundation of Zhejiang Province(No.LY22E020002).
文摘Near-infrared(NIR)luminescence materials are ideal candidates for applications in three-dimensional biomedical imaging and night vision.Here,we constructed an ultra-broadband NIR material based on LiBaF3:Ni^(2+)single crystals with NIR emission at 1400 nm and a full width at half maximum(FWHM)of 254 nm from 1100 to 1700 nm wavelengths,covering the NIR-II and NIR-Ⅲ regions.Through the activation of inactive Mg^(2+),the NIR emission could be improved by a factor of two,and the FWHM enhanced to 273 nm.This is ascribed to the lattice distortion by the addition of Mg^(2+)as well as the charge asymmetry between the Mg^(2+)and Li+ions.The prepared Ni^(2+)/Mg^(2+)-doped NIR perovskite single crystals were packaged with a commercial high-efficiency near-ultraviolet LED chip(@395 nm)to construct NIR single-crystal LEDs,and their promising applications with high efficiency were demonstrated in NIR night-vision monitoring and vein non-destructive imaging.
基金supported by the Liaoning Revitalization Talents Program(Grant No.XLYC2403017)the Natural Science Foundation of the Education Department of Liaoning Province(Grant No.JYTMS20231627)the Young Talents Program of Jinzhou(Grant No.JXYC230103).
文摘Short-wave infrared(SWIR)phosphor-converted light-emitting diodes(pc-LEDs)are promising for biomedical and nondestructive applications.Still,their progress is constrained by the lack of efficient,ultra-broadband phosphors excitable by low-cost blue LEDs.Cr^(3+)-activated materials exhibit strong blue light excitation,but their emission is primarily confined to the NIR-I region.In contrast,Ni^(2+)has the potential to achieve SWIR emission,yet suffers from weak absorption in the blue-light region.In this study,Y_(3)Al_(3)MgSiO_(12):Ni^(2+)and Y_(3)Al_(3)MgSiO_(12):Cr^(3+)–Ni^(2+)phosphors were synthesized.Compared to previous reports,the Y_(3)Al_(3)MgSiO_(12):Cr^(3+)–Ni^(2+)phosphor in this study achieved three significant advancements:(1)efficient energy transfer from Cr^(3+)to Ni^(2+)was achieved(η=91.6%),resulting in a 10.45-fold enhancement of SWIR emission intensity upon 438 nm blue-light excitation,and the optimal excitation wavelength was shifted to the blue-light region.(2)Ultra-broadband continuous emission spanning the NIR-I to NIR-III regions,with an exceptionally wide FWHM(185+311 nm),was achieved in this phosphor.(3)Remarkably high thermal stability was achieved for the NIR-II–III emission in a region where strong electron–phonon coupling and poor thermal stability are typically observed.The underlying mechanism was elucidated through analysis of the crystal structure rigidity and the Huang–Rhys factor(S).A SWIR pc-LED device was further fabricated by integrating the phosphor with a 450 nm blue LED chip,confirming its application potential in covert information recognition and nondestructive detection scenarios.This study not only introduces a broadband SWIR-emitting material system excitable by blue light but also provides a novel strategy for developing efficient and thermally stable SWIR phosphors.
基金supported by the National Key R&D Program of China(No.2021YFB3500400)National Natural Science Foundation of China(No.11904363)the Key Research Program of the Chinese Academy of Sciences(No.ZDRW-CN-2021-3).
文摘In recent years,near-infrared phosphor-converted light emitting diodes(NIR pc-LEDs)have been emerging as a promising compact and efficient NIR light source for a variety of applications such as sensing,bioimaging and food analysis.However,the development of broadband NIR phosphors with both high emission efficiency and excellent photoluminescence(PL)thermal stability is still facing a great challenge.
基金supported by the Guangxi NSF project(no.2020GXNSFDA238004)the“Guangxi Bagui Scholars”fund,the Guangxi Science and Technology Major Project(AA23073018)+1 种基金the Scientific and Technological Bases and Talents of Guangxi(Guike AD21238027 and AD23026119)for financial supportThe calculation was supported by the highperformance computing platform of Guangxi University。
文摘Realizing Sb^(3+)-activated efficient broadband near-infrared(NIR)emission under blue light excitation remains a significant challenge in lead-free metal halides.To overcome the above difficulties,a coordination structure modulation strategy was adopted,and the broadband NIR emission under blue light excitation was achieved in Sb^(3+)-doped zero-dimensional(0D)organic tin(Ⅳ)bromide.
基金Natural Science Foundation of Shanxi Province(20210302123056)Shanxi Provincial Key Research and Development Project(202102040201007,202203021223005)National Natural Science Foundation of China(52275577,52205609).
文摘High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared source structure based on an electron-phonon coupling and emitting mechanism.A series of electrical characterizations including carrier mobility[11,361.55 cm^(2)/(V.s)],pulse current(30 ms response time),and cycling stability(2000 cycles)modulated by polarized film was provided.
基金supported by the National Natural Science Foundation of China(Grant No.12104231,12364051,22303031)Innovation Training Program for College Students in Nanjing Forestry University(Grant No.202410298184Y)。
文摘The enduring enigma surrounding the near-infrared(NIR)emission of Mn^(2+)continues to ignite intense academic discussions.Numerous hypotheses have emerged from extensive research endeavors to explain this phenomenon,such as the formation of Mn^(2+)-Mn^(2+)ion pairs,Mn^(2+)occupying cubically coordinated sites,as well as conjectures positing the involvement of Mn3+oxidized from Mn^(2+)or defects.Despite these diverse and valuable insights,none of the hypotheses have yet achieved broad consensus.In this study,we have observed prolonged fluorescence lifetimes(~10ms)for the NIR emissions of Mn^(2+)ions,hinting at these ions occupying the high-symmetry octahedral sites inherent to the garnet lattice.This inference is supported by the corroborating results from X-ray absorption fine structure analysis and first-principles calculations.The intense crystal field of octahedral sites,similar to that of AlO6,facilitates the splitting of d-d energy levels,thereby inducing a red-shift in the emission spectrum to the NIR region due to the transition ^(4)T_(1)(4G)→ ^(6)A_(n)(6S)of isolated Mn^(2+).Our findings not only offer a plausible rationale for the NIR emission exhibited by other Mn^(2+)-activated garnet phosphors but also pave a definitive route towards understanding the fundamental mechanisms responsible for the NIR emission of Mn^(2+)ions.
文摘Unidentified Infrared emission bands (UIBs) are infrared discrete emissions from circumstellar regions, interstellar media (ISM), star-forming regions, and extragalactic objects for which the identity of the emitting materials is unknown. The main infrared features occur around peaks at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with the photon’s rest energy at the peaks 0.376, 0.200, 0.161, 0.144, 0.111, and 0.098 eV, respectively. The UIB emission phenomenon has been studied for about forty five years. The prevailing hypothesis is that the materials responsible for UIB are polycyclic aromatic hydrocarbon (PAH) molecules. PAHs are thought to be one of the main forms in which carbon exists in space. And yet, not a single member of this group of compounds had been identified in space definitively until now [1]. In frames of Hypersphere World-Universe Model (WUM), we introduced Dark Matter (DM) particles, named DIONs, with the rest energy 0.199 eV and an energy density of 68.8% of the total energy density of the World. DIONs compose Outer shells of DM Supercluster’s Cores—the main objects of the World [2]. In this paper, we give an explanation of UIB emission based on the self-annihilation of DM particles DIONs and biDIONs (DIONs pairs) with a rest energy about 0.38 eV that depends on the binding energy. To the best of our knowledge, WUM is the only cosmological model in existence that is consistent with UIB emission phenomenon.
基金Project supported by the National Natural Science Foundation of China (Grant No.51202291)
文摘A thin radar-infrared stealth-compatible structure with reflectivity below -10 dB in the whole radar X wave band and infrared emissivity less than 0.3 in the infrared region of 8μm-14 μm is reported. The designed stealth-compatible structure consists of metallic frequency selective surface （MFSS）, resistive frequency selective surface （RFSS）, and metal backing from the top down, and it is only 2. l-mm thick. The MFSS is made up of some divided low infrared emissivity metal copper films, and the RFSS consists of a capacitive array of square resistive patches. They are placed close together, working as an admittance sheet because of a mutual influence between them, and the equivalent admittance sheet greatly reduces the thickness of the whole structure. The proposed stealth-compatible structure is verified both by simulations and by experimental results. These results indicate that our proposed stealth-compatible structure has potential applications in stealth fields.
基金Project supported by the National Key Technology R&D Program(2011BAE30B04)University Innovation Team Leader Training Program in Hebei Province(LJRC020)
文摘A kind of far infrared radiation ceramics was prepared by using silicate minerals, calcium carbonate and silicon dioxide as main raw materials, and cerium nitrate as additive. The structure of the ceramics and far infrared radiation properties on the surface tension of water were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and a tensiometer, respectively. It was showed that, after being sintered at 1160 ℃, the solid solution was formed by CeO2 and Fe2O3, thus the crystal parameters （c/a axis ratio） and interplanar spacing of Fe2O3 increased. The addition of cerium was regarded to improve the far infrared radiation of ceramics, and the maximum emissivity value in the range of 5-20 μm was 0.94. The surface tension of water gradually decreased with increasing radiation time.
基金supported by the National Natural Science Foundation of China under Grant Nos.51772027 and 51972089。
文摘LaMgAl_(11)O_(19)(LMA),characterized by high melting point,low density and thermal conductivity as well as good infrared emissivity,is regarded as a potential candidate for the thermal protection of hypersonic vehicles.Nevertheless,the unsatisfied phase stability at high temperature results in declining of the emissivity below 6μm,which limits the extensive applications of LaMgAl_(11)O_(19).In order to overcome this obstacle,three dense bulk high-entropy ceramics,(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Dy_(0.2))Mg Al_(11)O_(19)(HE LMA-2)and La(Mg_(0.2)Fe_(0.2)Co_(0.2)Ni_(0.2)Zn_(0.2))Al_(11)O_(19)(HE LMA-3),were designed and successfully prepared through solid state reaction at 1700℃for 4 h in one step.XRD analyses show that the phase compositions of HE LMA-1,HE LMA-2 and HE LMA-3 are single-phase solid solutions with the relative density of 95.61%,95.49%and 94.31%,respectively.Heat treatment experiments demonstrate that the phase composition of HE LMA-1 remains a single phase after high-temperature heating,while second phase appears in other two samples.The stability of HE LMA-1 is attributed to small average size differenceδ(~4%)of constitute elements.Intriguingly,the average emissivity of HE LMA-1 in the range of 3-6μm reaches 0.9,which is significantly higher than that of LMA and other two HE LMA samples.The emissivity of all samples remains above 0.95 from 6 to 10μm.In the far infrared region(10-14μm),although the emissivity of these specimens decreases slightly,it still exceeds 0.85.The UV-Vis absorption spectra indicate that the formation of many discrete impurity energy levels with small intervals in HE LMA-1 promotes the f electrons to transit between adjacent impurity energy levels and conduction band,which enhances the infrared emission of HE LMA-1 below 6μm.In a word,with improved phase stability and thermal emissivity in infrared range,high-entropy REMgAl_(11)O_(19),especially(La_(0.2)Nd_(0.2)Gd_(0.2)Sm_(0.2)Pr_(0.2))MgAl_(11)O_(19)(HE LMA-1),is a promising candidate in thermal protection coatings of hypersonic vehicles.
基金Funded by the Scientific and Technological Research Projects for Education Department of Hubei Province(Q20161407)
文摘NiCr2O4（NCO）spinel composites with different Mn/Ni atomic ratios（Mn/Ni=0.05,0.10,0.15,and 0.20）were synthesized via solid state reaction method.Phase compositions and microstructure of samples were characterized by X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The TG-DSC curves showed that the appropriate baking temperature for Mn-doped NCO spinel preparation was approximately 1 320℃.X-ray diffraction patterns exhibited the formation of NCO spinel with Fd-3m space group.Valence state of the Mn ions was determined from 2p and 3s X-ray photoelectron spectra.Manganese ions were mostly in divalent and trivalent states,and the ratio of Mn^2＋/Mn^3＋was 0.78-0.98.Fourier transform infrared spectroscopy（FTIR）was used to analyze the spectral emissivity of Mn doped NCO spinel.It was revealed that the infrared emissivity of Mn-doped NCO spinel in 1.8-5μm could be significantly enhanced with increasing content of Mn^2＋,reaching as high as 0.9398.Mn-doped NCO spinel showed excellent radiation performance and good prospect in high emissivity applications in the temperature range of 800-1 200℃.
基金This work was financially supported by the National Natu-ral Science Foundation of China(Nos.51972082,51972089,and 52172041)the Key Program of National Natural Science Foun-dation of China(No.52032003).
文摘Transition metal disilicides are widely used as heating elements and infrared emission coatings.However,the limited intrinsic infrared emissivity and high thermal conductivity are the main limitations to their applications as infrared emission coatings in the thermal protection system.To cope with these prob-lems,four medium and high-entropy transition metal disilicides,i.e.,(V_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-1),(Nb_(0.25)Ta_(0.25)Mo_(0.25)W_(0.25))Si_(2)(ME-2),(V_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-1),and(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2),were designed and synthesized by spark plasma sintering method using transition metal binary disilicides as precursors.The introduction of multi-elements into transition metal disilicides not only im-proved the infrared emissivity but also reduced the electrical and thermal conductivity.Among them,(Cr_(0.2)Nb_(0.2)Ta_(0.2)Mo_(0.2)W_(0.2))Si_(2)(HE-2)had the lowest electrical conductivity of 3789 S cm-1,which is over one order of magnitude lower than that of MoSi_(2)(50000 S cm^(-1)),and total infrared emissivity of 0.42 at room temperature,which is nearly double of that of TaSi_(2).Benefiting from low electrical conductivity and phonon scattering due to lattice distortion,the medium and high-entropy transition metal disilicides also demonstrated a significant decline in thermal conductivity compared to their binary counterparts.Of all samples,HE-2 exhibited the lowest thermal conductivity of 6.4 W m^(−1)K^(−1).The high-entropy tran-sition metal disilicides also present excellent oxidation resistance at high temperatures.The improved infrared emissivity,reduced thermal conductivity,excellent oxidation resistance,and lower densities of these medium and high-entropy transition metal disilicides portend that they are promising as infrared emission coating materials for applications in thermal protection systems.
基金the National Natural Science Foundation of China (52273083, 51903145)Key Research and Development Project of Shaanxi Province (2023-YBGY-476)+1 种基金Natural Science Foundation of Chongqing,China (CSTB2023NSCQ-MSX0691)National College Students Innovation and Entrepreneurship Training Program (202310699172)
文摘Lightweight infrared stealth and absorption-dominant electromagnetic interference(EMI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable electronics.Herein,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EMI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding strategy.The obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EMI shielding performances attributed to the synchronous construction of microcellular structures and segregated structures.Particularly,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved EM wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.Moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression cycles.The results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EMI shielding applications in aerospace,weapons,military and wearable electronics.
基金Project(JB141405)supported by the Fundamental Research Funds for the Central Universities of China
文摘Alkali metal(Li, Na, K) doped ZnO powders were synthesized by solid-state reaction at different calcination temperatures and holding time. Effects of holding time and K sources on the infrared emissivity of ZnO were investigated. The structure and surface morphologies of samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The UV-Vis absorption and infrared emissivities were investigated by a UV-Vis spectrophotometer and an infrared emissometer, respectively. XRD patterns confirm the wurtzite structure of the as prepared samples with single phase. Smooth grain surfaces are detected in all doped ZnO samples, while ZnO:Li and ZnO:Na present the aggregation of grains. The redshifts in the optical band-gap are observed in K-, Na-, and Li-doped ZnO with the values 3.150, 3.144, and 3.142 eV. Due to better crystalline quality, ZnO:K shows a lower emissivity than others. The emissivity of K-doped ZnO decreases to the minimum value(0.804), at 1200 °C and holding 2 h. Compared with KNO3 as K source, K2CO3 doped ZnO has lower emissivities.
文摘Infrared emissivities of Zn0.99-xMn0.01CoxO （x = 0.00, 0.01, 0.03, 0.05） powders synthesized at different calcination temperatures by solid-state reaction are investigated. Their phases, morphologies, UV absorption spectra, and infrared emissivities are studied by XRD, SEM, UV spectrophotometer, and an IR-2 dual-band infrared emissometer in a range of 8 μm-14 μm. Doped ZnO still has a wurtzite structure, and no peaks of other phases originating from impurities are detected. The optical band-gap decreases as the Co content and calcination temperature ascend, and of which the smallest optical band gap is 2.19 eV. The lowest infrared emissivity, 0.754, is observed in Zn0.98Mn0.01Co0.01O with the increase in Co concentration. The infrared emissivity experiences fluctuations as the calcination temperature increases, and its minimum value is 0.762 at 1100 ℃.
文摘The stoichiometric vanadium（IV） oxide thin films were obtained by controlling the temperature, time and pressure of annealing. The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 nm VO2 thin films in the 7.5 μm-14 μm region were discussed. The derived VO2 thin film samples were characterized by Raman, XRD, XPS, AFM, SEM, and DSC. The resistance and infrared emissivity of VO2 thin films under different temperature were measured, and the thermal images of films were obtained using infrared imager. The results show that the VO2 thin film annealed at 550 ℃ for 10 hours through aqueous sol-gel process is pure and uniform. The 900 nm VO2 thin film exhibits better IR thermochromic property than the 400 nm VO2 thin film. The resistance of 900 nm VO2 film can change by 4 orders of magnitude and the emissivity can change by 0.6 during the phase transition, suggesting the outstanding IR thermochromic property. The derived VO2 thin film can control its infrared radiation intensity and lower its apparent temperature actively when the real temperature increases, which may be applied in the field of energy saving, thermal control and camouflage.
